Aspirators connecting a vacuum source to a nozzle having a hollow tip are widely used in a plurality of professional fields and, namely, in the medical field. In dentistry, for instance, aspirators are used by dentists or hygienists and dental assistants for aspirating saliva, blood, water and debris from the patient's mouth during a treatment or surgery. The aspirating tool and the user thereof have to deal with opposite concerns in such an application.
Firstly, all liquid, solid particles and aerosols must be extracted in an effective manner, due to the health hazards they represent. The risks for the patient and the medical personnel tend to increase with the increasing use of high technology materials such as polymers and composites yielding toxic resin vapours and microscopic particles of silicium, quartz etc. when shaped with rotary instruments, cut, abraded or polished. These materials are often used for replacing silver amalgam fillings which, when deposited mechanically, produce toxic mercury vapours. Therefore, relatively strong suction and heavy airflow are desirable. However, contact of the aspirator tip aperture with the tongue or other delicate mouth tissues tends to block airflow, yielding a rapid negative pressure increase firmly grabbing the tissue against the aperture, and causing discomfort and risks of injury for the patient and stress both for the patient and the medical personnel. For that type of reasons, a vacuum release vent is now often provided on medical aspirators.
The vacuum release vent is generally an auxiliary bypass orifice, smaller than the main suction port, provided along the aspirating line, which enables penetration of air into the suction line with some restriction when air intake is obstructed at the main port, thus preventing vacuum inrush and water hammer effects. An early design of such a vented aspirator is described in U.S. Pat. No. 3,516,160 issued to Leffler in June 1970, which introduces the Tip-A-Dilly™ aspirator 100 illustrated in FIG. 4 of the appended drawings. The aspirator 100 includes a body 103 provided with two bypass orifices 101, 102 and terminated at its upstream end by a portion 105 provided with a main inlet bore 107 connected to a suction tip 106, and at its downstream end by an outlet portion 104 for connection to a vacuum hose. In operation, when vacuum is applied at outlet 104, a fluid stream 108, typically containing air, body fluids and solid debris, is created in the main inlet 107. At the same time, air from the surrounding atmosphere enters the body 103 through orifices 101, 102 and merges with the main stream 108 to exit the device at outlet 104 as mixed fluid stream 109.
Should the inlet of tip 106 be blocked by contact with body tissues for instance, the thereby modified ratio between the tip inlet effective cross-section and that of the bypass orifices 101, 102, will automatically cause more air to be drawn through these orifices to prevent sudden increase of suction rate at the tip and firm grabbing of the tissues. However, air penetrating at high velocity through the small orifices in the inner chamber of the body 103 experiences turbulence due to rapid expansion at the inner side of the orifices and sharp edges at the interface between the inner chamber of the body 103 and the outlet portion 104. Turbulence creates acoustic waves tuned by the resonant cavity provided by the inner chamber, thus generating a hissing noise.
Other examples of such vented medical aspirators are described in U.S. Pat. No. 5,425,637 (Whitehouse et al.—June 1995), U.S. Pat. No. 5,509,802 (Whitehouse et al.—April 1996), U.S. Pat. No. 5,542,929 (Laabs et al.—August 1996) and U.S. Pat. No. 5,964,733 (Laabs et al.—October 1999).
Noise in medical aspirators, particularly dental aspirators used extensively and repeatedly by dentistry personnel, is recognized as a very significant problem. Indeed, it is a source of fatigue, stress accumulation and it represents a real risk of hearing acuity degradation for medical personnel. This noise problem has been specifically addressed in U.S. Pat. No. 5,195,952 issued to Solnit et al. in March 1993 which introduces the Grab Free™.
As illustrated in FIG. 5, the Grab Free™ is a device 100 which includes a plurality of tiny elongated bypass ports 111, 112 in the solid body 113. The body 113 includes an outlet portion 114 and an inlet portion 115 with a lip 116 for insertion of a removable suction tip. The main fluid which flows from the suction tip enters the main inlet 117 which has a constant cross-section port up to the outlet of the device. Upon clogging of the main inlet, air is drawn through the bypass ports and merges smoothly with the main flow due to the acute angle of incidence. Therefore, fluid streams follow smooth paths and merge as combined flow 119 at the outlet of the device with minimal separation, turbulence and resonance, leading to a significantly reduced noise level. However, the concept of this device provides fixed vacuum compensation and does not allow the user to block one or more of bypass ports 111, 112 to control the aspiration rate at the tip. Also, the weight of the solid metal body 113 at the downstream end of the device 110 adds to that of the vacuum hose and connector to create a moment of rotation about the user's wrist, yielding physical fatigue and discomfort of the user, to compensate the lift of the aspiration tip.
Suction control is indeed a desirable feature in aspirators used in dentistry as well as in many medical fields related to surgery, in lipectomy surgery or draining of wound fluids for instance. One may thereby avoid subjecting delicate tissues to too strong a suction force while properly performing aspiration of specific matters as needed. Therefore, some aspirator systems of the prior art justify and describe suction control or regulator devices of two types. In a first type, a venting port of relatively small effective area can selectively be either left open to provide a definite level of suction or blocked by a sleeve or a finger to momentarily increase suction, or vice versa. U.S. Pat. No. 4,534,542 (Russo—August 1985), U.S. Pat. No. 5,855,562 (Moore et al.—January 1999), U.S. Pat. No. 5,975,897 (Propp et al.—November 1999) and U.S. Pat. No. 6,045,516 (Phelan—April 2000), as well as Canadian patent No 2,042,523 (Nates—Oct. 1995) exemplify that first type of controlled vacuum aspirators.
Fewer suction control devices of a second type are so designed to enable a user to continuously vary suction over a given range. Representative examples of aspirators implementing such suction control devices are described in U.S. Pat. No. 4,221,220 (Hansen—September 1980), U.S. Pat. No. 5,013,300 (Williams—May 1991), U.S. Pat. No. 5,730,727 (Russo—March 1998), U.S. Pat. No. 5,899,884 (Cover et al.—May 1999) and U.S. patent application No. 2002/0108614A1 filed by Schultz in April 2002.
The published patent application by Schultz, which is illustrated in FIG. 6, teaches a hand-held medical component which is provided with a wide elongated port for regulating suction. Suction is provided from a device which comprises a body 123 with an inlet portion 125 and an outlet portion 124 for connection to a vacuum source. The device is further provided with a large opening and relatively large throat bypass inlet penetrating the body up to the inner chamber 122. The large elongated opening of the bypass inlet 121 is so designed as to enable a user to control the suction rate at the inlet of suction tube 126 by selectively blocking a variable portion of said opening with a finger. Although such a feature is highly desirable in many applications, noise with such a device is still a major problem which prevents its extensive use in applications such as dentistry. Indeed, the main fluid stream 128 rapidly expands and separates when passing from the inlet 125 to the chamber 122 of much larger cross-sectional area. Similarly, the pressure compensating air flow penetrating the chamber from inlet 121, experiences separation and turbulence due to the orthogonal incidence when merging into the main stream and to the sharp edges present at the interface. Therefore, the main and bypass flows could not merge to form an outlet fluid stream 129 without generating a highly noisy acoustic emission tuned according to the dimensions of chamber 122 and because of the resonant cavity yielding flow separation, turbulence, acoustic amplification and, consequently, intense irritating noise.
With the exception of the Solnit Patent, all of the aforementioned patents have their bypass inlet extending straight through the outer wall of the aspirator body such that the incoming airflow substantially forms a right angle with respect to the fluid stream in the main bore of the device. Also, none of the auxiliary aperture shapes have been specifically designed in consideration of the aero-acoustic concerns for optimal merging of the bypass air flow from atmosphere with the main fluid stream, that is with minimal energy being dissipated and converted into sound waves, and minimal transfer of said sound waves to the surrounding work environment.
Although the above examples show that some suction control bypass devices and controlled aspirating devices are contemplated in the prior art, these devices are nevertheless lacking important features necessary for them to provide adequate control of aspiration rate as required in medical applications for instance, while generating low level minimally annoying noise.
It would therefore be a significant advance in the art of controlled suction aspirating devices to provide a low-noise suction control device and an aspirator using such a device, which can be advantageously controlled with a user's finger or sliding sleeve to provide a wide range of aspiration rates, while generating low and minimally annoying noise, according to preferred structures as contemplated in the present invention. It would also be desirable to provide an aspirator which enhances the physical comfort of a user through an ergonomic design providing weight balance and natural and adjustable tip angulations.